Device for trisecting angles



Sept. 28, 1948.

G. c. ROBINSON 2,450,167

DEVICE FOR TRISECTING ANGLES Filed 001:. 14, 1946 Inventor WWW Patented Sept. 28, 1948 UNITED STATES PATENT OFFICE 2,450,167 llEVICE FOR TRISECTING ANGLES George C. Robinson, Los Angeles, Calif. Application October 14, 1946, Serial No. 703,225

4 (llaims.

This invention relates to new and useful improvements and structural refinements in geometrical devices, and the principal object of the invention is to provide an instrument or device of the character herein described, which may be conveniently and effectively employed for the accurate trisection of angles. I

A further object of the invention is to provide a device for trisecting angles which is entirely of a mechanical nature and the use of which does not involve mathematical calculation or the reading of graduated scales.

Another object of the invention is to provide a device for trisecting angles which is simple in construction, convenient and accurate in use, and which may be applied to angles of various magnitudes. l

An additional object of the invention is to provide a device for trisecting angles which will not easily become damaged and which will readily lend itself to economical manufacture.

A still further object of the invention is to provide a device for trisecting angles which is otherwise well adapted for the purpose for which it is intended.

With the above more important objects in view,

and such other objects as may become apparent as this specification proceeds, the invention consists essentially of the arrangement and construction of parts as illustrated in the accompanying drawings, in which:

Figure 1 is a plan View of the invention.

Figure 2 is a side elevation thereof.

Figure 3 is an underside perspective view of a cursor used in the invention, and

Figure 4.- is a cross sectional view, taken substantially in the plane of the line 4-4 in Figure 1.

Like characters of reference are used to desi nate like parts in the specification and throughout the several views.

Referring now to the accompanying drawings in detail, the invention consists of a device for trisecting angles designated generally by the reference character ID, the same embodying in its construction a blade II provided at one end thereof with a substantially semi-circular, laterally projecting protuberance I2. It will be noted that the geometric center of this protuberance is disposed substantially in the projected plane of one of the longitudinal edges I3 of the blade, and a tapered bore I4 is formed at the center of the protuberance, as is best shown in Figure 4.

The bore I4 is adapted to receive a complementarily tapered head of a pivot pin 15, the latter also including a shoulder I6 of relatively reduced diameter, and a further reduced, screw threaded shank I1.

The pivot pin I5 is also provided with a longitudinally extending bore I8, and it should be particularly noted that the axis of this bore is disposed in the projected plane of the aforementioned edge I3.

An arm I9 is of a substantially similar configuration to the blade I I, including the protuberance 20 formed at one end of the arm. However, the arm I9 is of a substantially lesser width with respect to the blade and the protuberance 20 is formed with a suitable aperture, whereby the arm may be pivotally mounted upon the shoulder I6 of the pin l5. A suitable nut 2 I, positioned on the threaded shank IT, is employed for securing the arm and blade together.

Particular attention is also directed to the fact that'the axis of the bore I8 is also disposed in the projected plane of the longitudinal edge 22 of the arm I9, in other words, the edges I3 and 22 radiate, so to speak, from the axis of the bore I8, as will be clearly understood.

A cursor 23 is slidably positioned on the arm I9, this being facilitated by the provision of a bore 24 in the cursor, wherein the arm is slidably received. The cursor is of a substantially T-shaped configuration as shown in the drawings, and includes what may be referred to as a head 25, provided a longitudinal edge or surface 26.

Suirtable' spring clips 21 may be provided in the bore 24 for resisting the sliding of the cursor upon the arm l9, and the free end of the latter may also be equipped with a pin or stop 28, to prevent the separation of the cursor and arm.

It should be emphasized at this point that the longitudinal edge 26 is equal in length to twice the width of the blade II and that the distance from the end 28 of the edge 26 to the longitudinal edge 22 of the arm I9 is exactly equal to the width of the blade II. In other words, the edge 22 passes through the exact center of the edge 26 and the latter, if desired, may be inscribed with a transversely extending index line 29 to indicate the center in the length of the edge (26) It may be also noted that the line 29 is coplanar with the projected plane of the longitudinal edge 22.

It should be also noted that the respective thicknesses of the components II, I9 and 23 are such that the device will lie fiat upon the surface upon which it is positioned, that is, the lower surface of the cursor 23 is disposed in the plane of the lower surface of the blade II, as is best shown in Figure 2.

The entire device may be constructed from transparent material, such as lucite, and if desired, the blade I I may be formed with a plurality of lightening apertures 30.

The manner in which the invention is used is illustrated in the accompanying Figure 1, wherein it is required to trisect the angle 3| included between the lines 32 and 33.

The device is applied so that the axis of the bore [8 is coincident with the intersection of the lines 32, 33, and a pencil point or a thumb tack may be inserted into the bore l8, to assure this condition.

The blade II is then adjusted so that the edge I3 thereof coincides with the line 32, whereupon the arm I9 is adjusted with respect to the blade and the cursor 23 is adjusted with respect to the arm, so that the end 28 of the cursor contacts the remaining longitudinal edge 34 of the blade H, while the relatively opposite end 35 of the cursor is disposed on the line 33.

Markings may now be made as to the position of the index line 29 and of the cursor edge or end 28, these markings, when subsequently projected from the intersection of the lines 32 and 33, producing the lines 36 and 31. It will be found that the lines 36 and 31 trisect the angle 3| into three equal angles 38, 39 and 40.

It is believed that the advantages and use of the invention will be clearly understood from the foregoing disclosure and accordingly, further description thereof at this point is considered unnecessary.

While in the foregoing there has been shown and described the preferred embodiment of this invention it is to be understood that minor changes in the details of construction, combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as claimed.

What I claim as my invention is:

4 V 1. A device for trisecting angles, comprising in combination, a blade, a pivot adjacent one end of said blade, an arm mounted adjacent one end thereof on said pivot, one longitudinal edge of said arm and one longitudinal edge of said blade radiating from said pivot, and an elongated cursor slidable on said arm, one longitudinal edge of said cursor being equal in length to twice the width of said blade and extending at right angles to said arm, one end of said cursor being engageable with the remaining longitudinal edge of said blade.

2. The device'as defined in claim 1, together with a transversely extending index line inscribed on said longitudinal edge of said cursor, said line being coplanar with said longitudinal edge of said arm.

3. In a device for trisecting angles, a blade having parallel longitudinal edges, an arm, a pivot connecting said arm to said. blade, one longitudinal edge of said blade and one longitudinal edge of said arm extending radially from said pivot, and a cursor slidable on said arm, said cursor having an edge equal in length to twice the width of said blade and disposed at right angles to said arm, one end of said edge of said cursor being engageable with the remaining longitudinal edge of said blade.

4. The device as defined in claim 3 wherein said pivot is formed with an axially extending sight.

GEORGE C. ROBINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France May 15, 1913 

